NIF Panic with duplicated key in rename

[pcapel]

Overview

It's a nit pick, but a NIF panic is a surprising error when a key is duplicated in the DataFrame.rename function. A more descriptive error would make a lot of sense.

It looks like there already some validation where this could fit in, happy to add support if this is deemed worthwhile.

Minimal reproduction via the livebook below.

Reproduce Panic

Mix.install([
  {:explorer, "~> 0.8.0"}
])

Section

alias Explorer.DataFrame, as: DF
require Explorer.DataFrame

Explorer.DataFrame

DF.new(%{key1: [1, 2, 3, 4], key2: [5, 6, 7, 8]})
|> DF.rename(
  key1: "first_key",
  key1: "second_key"
)

[pcapel]

I see that the linked function is for the rename which is acting against all columns. The reproduction would use the other clause, which is where the check would need to happen. Thinking something similar to maybe_raise_column_not_found?

[billylanchantin]

I agree we should validate before we pass off to Polars.

Old contents

Also, I think there's a bug in the validation code?

https://github.com/elixir-explorer/explorer/blob/main/lib/explorer/shared.ex#L225-L234

This

unless Map.has_key?(df.dtypes, name) do
#                   ^^^^^^^^^

should be

unless Map.has_key?(df.names, name) do
#                   ^^^^^^^^

right?

EDIT: No I was wrong about there maybe being a bug.